I did it for 4 months - and ended u with a stash in the freezer which made enough milk for 6 months, which covered weaning foods too 
And...controversially...I plan to do it again.
For me, it was just a damn sight easier (the hardest part for me was arguing with others that it couldn't possibly be).
Ds was a very very big boy and initially he was on the boob for HOURS with no let up and still starving. It was really rough going.
I had emcs, was sore, knackered and really needed a chill out, plus dh had only a week off work, so I started expressing so I could get some sleep. And never looked back.
I got loads and loads of milk - I mean tons. I found bags of it in the freezer before we moved house that I had forgotten were there.
Maybe I was lucky, but it completely worked for me. DH was very involved (he would feed ds while I pumped during the night), or I would pump straight after feeding.
It meant I could do things like catch up on much needed sleep (which aided my recovery), dh and I got some much needed time out together, grandparents/cousins/friends etc could feed ds (nothing nicer than feeding a baby), we knew how much he ate, he got a good routine going from early and slept through the night at a young age....
Like I say, perhaps we were just lucky, but it worked for us.
We got zip support for doing this from midwives who reckoned we were just 'making ore work for ourselves' and yes, I cracked up about it a few times - was made to feel like a poor mother for doing it this way. In the end my mum had to remind me that he was my baby and I was the one who had to do it, not them, and if it worked for me, then bugger them!!
This time I am not going to feel guilty about it.
I shall be expressing with pride!!